1. Field of the Invention
This invention relates to a metal deck-concrete composite slab structure of the type used in floors and roofs. More specifically, this invention relates to such a composite slab structure having an integrally formed concrete transverse reinforcing beam which permits longer longitudinal spans between adjacent transverse load bearing support walls.
2. Description of the Prior Art
In building construction, economical, strong and durable floor and roof constructions often incorporate an integrally reinforced metal deck member which has an overlying layer of concrete. Such structures frequently have metal deck elements which have integral reinforcement in the form of upwardly projecting hollow ribs with the concrete provided thereover in complementary surface to surface engagement therewith. See U.S. Pat. Nos. 1,073,540, 1,574,586, 1,828,842 and 1,975,842. The interengagement between the metal deck and concrete provides a permanently joined, field created composite slab which will withstand substantial loads without failure or excessive deformation.
As there is a maximum safe length of longitudinal span for such structures, transverse support such as continuous load bearing walls must be provided within predetermined maximum longitudinal span limits. Such limits are established on the basis of gage of the metal in the metal deck, height of the hollow rib, concrete weight per cubic foot, total composite slab depth and desired allowable load on the composite slab. For a given set of conditions, the maximum longitudinal unsupported span serves to create a restriction on flexibility of building design. The span limit prevents the creation of rooms with larger dimensions between load bearing support walls (or other interfering support members, such as transverse structural steel members which limit head room and must be enclosed at added expense). While not directed toward composite slab structures, the awkwardness of enclosing such reinforcing members in all-concrete structures is exemplified by U.S. Pat. Nos. 732,482 and 913,083 wherein all-concrete floors are formed with irregular thickness created by downwardly projecting steel member enclosures which are in turn supported by continuous load bearing walls.
There remains, therefore, a substantial need for an economical means of permitting longer longitudinal spans in composite slabs so as to permit greater design flexibility of building design and improved economy of construction. In addition, there is a particular need for such systems which facilitate the use of a composite slab having a generally uniform thickness between load bearing walls so as to simplify interior finishing, create greater structural symmetry and avoid mechanically and aesthetically undesirable irregular steel support means and enclosures which project downwardly into and partially obstruct the underlying space.